(a) Field of the Invention
The present invention relates to a method of post-correction of a 3D feature point-based direct teaching trajectory.
(b) Description of the Related Art
Vertical multi-jointed robots used for plant automation are used mainly for welding on an automotive assembly line, automatic transportation of industrial products, and general transportation because of its high velocity and reliability. In order to put these robots into practice, it is necessary to perform teaching, that is, to input a motion trajectory into the robots and so-called “teach” them. Currently, experts use a teaching device to program main trajectories of robots one-by-one. The operation of teaching an industrial robot is to simply program a desired trajectory, which may be considered a simple operation. However, it requires new programming each time according to the type of process in which the industrial robot is used. Also, even if the principle of programming a trajectory is the same, trajectory programming itself is highly complicated and takes a lot of time and effort (Y. Shamash, Y. Yang, and Z. Roth, “Teaching a Robot”, International Encyclopedia of Robotics: Applications and Automation, R. C. Dorf, Ed. Wiley, 1988, pp. 1689-1701).
Due to these problems, many studies have been recently done in an attempt to perform teaching in an intelligent manner, taking a break from the conventional teaching methods, and direct teaching is one of these studies (C. H. Park, J. H. Kyung, D. I. Park, K. T. Park, D. H. Kim, and D. G. Gweon, “Direct Teaching Algorithm for a Manipulator in a Constraint Condition using the Teaching Force Shaping Method”, Advanced Robotics, no. 24, pp. 1365-1384, 2010). The term “direct teaching” refers to a method in which a user teaches a robot a trajectory while directly holding a tip end of the robot and moving the robot along the trajectory. At this point, the rigidity of the joints of the robot needs to be properly decreased in order to allow the user to handle the joints with ease, and the trajectory needs to be recorded while the user performs direct teaching. Afterwards, the user directly teaches the robot at a point of time when the robot is used and operated in an actual process, thereby making the robot move along the recorded trajectory.
However, it is not easy to accurately record a teaching trajectory because of noise. In most cases, the original trajectory is severely damaged due to low-frequency noise caused by the user's hand shaking and trajectory distortion caused by the user's mistake of failing to properly estimate a trajectory at a corner, as well as usual high-frequency noise generated from a sensor and an electronic circuit. The high-frequency noise may cause an abnormal operation because it requires excessive velocity when reproducing the trajectory as taught, and the low-frequency noise may lead to a significant decrease in the accuracy of the reproduction of the teaching trajectory. However, a current solution, if any, to these problems is to use a line-smoothing algorithm to handle high-frequency noise.
As stated above, the direct teaching method still has a considerable amount of factors that may cause problems when applied to industrial fields. Hence, there are many studies ongoing at the moment to record a trajectory for direct teaching with more accuracy and allow a robot to accurately reproduce the recorded trajectory.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.